![Petr Mladek](/assets/img/avatar_default.png)
printk() takes some locks and could not be used a safe way in NMI
context.
The chance of a deadlock is real especially when printing stacks from
all CPUs. This particular problem has been addressed on x86 by the
commit a9edc88093
("x86/nmi: Perform a safe NMI stack trace on all
CPUs").
The patchset brings two big advantages. First, it makes the NMI
backtraces safe on all architectures for free. Second, it makes all NMI
messages almost safe on all architectures (the temporary buffer is
limited. We still should keep the number of messages in NMI context at
minimum).
Note that there already are several messages printed in NMI context:
WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE
handlers. These are not easy to avoid.
This patch reuses most of the code and makes it generic. It is useful
for all messages and architectures that support NMI.
The alternative printk_func is set when entering and is reseted when
leaving NMI context. It queues IRQ work to copy the messages into the
main ring buffer in a safe context.
__printk_nmi_flush() copies all available messages and reset the buffer.
Then we could use a simple cmpxchg operations to get synchronized with
writers. There is also used a spinlock to get synchronized with other
flushers.
We do not longer use seq_buf because it depends on external lock. It
would be hard to make all supported operations safe for a lockless use.
It would be confusing and error prone to make only some operations safe.
The code is put into separate printk/nmi.c as suggested by Steven
Rostedt. It needs a per-CPU buffer and is compiled only on
architectures that call nmi_enter(). This is achieved by the new
HAVE_NMI Kconfig flag.
The are MN10300 and Xtensa architectures. We need to clean up NMI
handling there first. Let's do it separately.
The patch is heavily based on the draft from Peter Zijlstra, see
https://lkml.org/lkml/2015/6/10/327
[arnd@arndb.de: printk-nmi: use %zu format string for size_t]
[akpm@linux-foundation.org: min_t->min - all types are size_t here]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> [arm part]
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
483 lines
14 KiB
C
483 lines
14 KiB
C
#ifndef __KERNEL_PRINTK__
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#define __KERNEL_PRINTK__
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#include <stdarg.h>
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#include <linux/init.h>
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#include <linux/kern_levels.h>
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#include <linux/linkage.h>
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#include <linux/cache.h>
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extern const char linux_banner[];
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extern const char linux_proc_banner[];
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static inline int printk_get_level(const char *buffer)
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{
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if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
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switch (buffer[1]) {
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case '0' ... '7':
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case 'd': /* KERN_DEFAULT */
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return buffer[1];
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}
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}
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return 0;
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}
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static inline const char *printk_skip_level(const char *buffer)
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{
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if (printk_get_level(buffer))
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return buffer + 2;
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return buffer;
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}
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#define CONSOLE_EXT_LOG_MAX 8192
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/* printk's without a loglevel use this.. */
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#define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
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/* We show everything that is MORE important than this.. */
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#define CONSOLE_LOGLEVEL_SILENT 0 /* Mum's the word */
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#define CONSOLE_LOGLEVEL_MIN 1 /* Minimum loglevel we let people use */
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#define CONSOLE_LOGLEVEL_QUIET 4 /* Shhh ..., when booted with "quiet" */
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#define CONSOLE_LOGLEVEL_DEFAULT 7 /* anything MORE serious than KERN_DEBUG */
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#define CONSOLE_LOGLEVEL_DEBUG 10 /* issue debug messages */
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#define CONSOLE_LOGLEVEL_MOTORMOUTH 15 /* You can't shut this one up */
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extern int console_printk[];
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#define console_loglevel (console_printk[0])
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#define default_message_loglevel (console_printk[1])
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#define minimum_console_loglevel (console_printk[2])
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#define default_console_loglevel (console_printk[3])
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static inline void console_silent(void)
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{
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console_loglevel = CONSOLE_LOGLEVEL_SILENT;
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}
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static inline void console_verbose(void)
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{
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if (console_loglevel)
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console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
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}
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struct va_format {
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const char *fmt;
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va_list *va;
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};
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/*
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* FW_BUG
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* Add this to a message where you are sure the firmware is buggy or behaves
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* really stupid or out of spec. Be aware that the responsible BIOS developer
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* should be able to fix this issue or at least get a concrete idea of the
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* problem by reading your message without the need of looking at the kernel
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* code.
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*
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* Use it for definite and high priority BIOS bugs.
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*
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* FW_WARN
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* Use it for not that clear (e.g. could the kernel messed up things already?)
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* and medium priority BIOS bugs.
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*
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* FW_INFO
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* Use this one if you want to tell the user or vendor about something
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* suspicious, but generally harmless related to the firmware.
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*
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* Use it for information or very low priority BIOS bugs.
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*/
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#define FW_BUG "[Firmware Bug]: "
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#define FW_WARN "[Firmware Warn]: "
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#define FW_INFO "[Firmware Info]: "
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/*
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* HW_ERR
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* Add this to a message for hardware errors, so that user can report
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* it to hardware vendor instead of LKML or software vendor.
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*/
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#define HW_ERR "[Hardware Error]: "
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/*
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* DEPRECATED
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* Add this to a message whenever you want to warn user space about the use
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* of a deprecated aspect of an API so they can stop using it
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*/
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#define DEPRECATED "[Deprecated]: "
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/*
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* Dummy printk for disabled debugging statements to use whilst maintaining
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* gcc's format checking.
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*/
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#define no_printk(fmt, ...) \
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do { \
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if (0) \
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printk(fmt, ##__VA_ARGS__); \
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} while (0)
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#ifdef CONFIG_EARLY_PRINTK
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extern asmlinkage __printf(1, 2)
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void early_printk(const char *fmt, ...);
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#else
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static inline __printf(1, 2) __cold
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void early_printk(const char *s, ...) { }
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#endif
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#ifdef CONFIG_PRINTK_NMI
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extern void printk_nmi_init(void);
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extern void printk_nmi_enter(void);
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extern void printk_nmi_exit(void);
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extern void printk_nmi_flush(void);
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#else
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static inline void printk_nmi_init(void) { }
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static inline void printk_nmi_enter(void) { }
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static inline void printk_nmi_exit(void) { }
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static inline void printk_nmi_flush(void) { }
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#endif /* PRINTK_NMI */
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#ifdef CONFIG_PRINTK
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asmlinkage __printf(5, 0)
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int vprintk_emit(int facility, int level,
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const char *dict, size_t dictlen,
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const char *fmt, va_list args);
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asmlinkage __printf(1, 0)
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int vprintk(const char *fmt, va_list args);
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asmlinkage __printf(5, 6) __cold
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int printk_emit(int facility, int level,
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const char *dict, size_t dictlen,
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const char *fmt, ...);
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asmlinkage __printf(1, 2) __cold
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int printk(const char *fmt, ...);
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/*
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* Special printk facility for scheduler/timekeeping use only, _DO_NOT_USE_ !
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*/
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__printf(1, 2) __cold int printk_deferred(const char *fmt, ...);
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/*
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* Please don't use printk_ratelimit(), because it shares ratelimiting state
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* with all other unrelated printk_ratelimit() callsites. Instead use
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* printk_ratelimited() or plain old __ratelimit().
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*/
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extern int __printk_ratelimit(const char *func);
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#define printk_ratelimit() __printk_ratelimit(__func__)
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extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
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unsigned int interval_msec);
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extern int printk_delay_msec;
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extern int dmesg_restrict;
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extern int kptr_restrict;
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extern void wake_up_klogd(void);
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char *log_buf_addr_get(void);
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u32 log_buf_len_get(void);
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void log_buf_kexec_setup(void);
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void __init setup_log_buf(int early);
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__printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...);
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void dump_stack_print_info(const char *log_lvl);
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void show_regs_print_info(const char *log_lvl);
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#else
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static inline __printf(1, 0)
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int vprintk(const char *s, va_list args)
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{
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return 0;
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}
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static inline __printf(1, 2) __cold
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int printk(const char *s, ...)
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{
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return 0;
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}
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static inline __printf(1, 2) __cold
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int printk_deferred(const char *s, ...)
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{
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return 0;
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}
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static inline int printk_ratelimit(void)
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{
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return 0;
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}
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static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies,
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unsigned int interval_msec)
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{
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return false;
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}
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static inline void wake_up_klogd(void)
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{
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}
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static inline char *log_buf_addr_get(void)
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{
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return NULL;
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}
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static inline u32 log_buf_len_get(void)
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{
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return 0;
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}
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static inline void log_buf_kexec_setup(void)
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{
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}
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static inline void setup_log_buf(int early)
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{
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}
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static inline __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...)
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{
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}
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static inline void dump_stack_print_info(const char *log_lvl)
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{
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}
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static inline void show_regs_print_info(const char *log_lvl)
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{
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}
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#endif
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extern asmlinkage void dump_stack(void) __cold;
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#ifndef pr_fmt
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#define pr_fmt(fmt) fmt
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#endif
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/*
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* These can be used to print at the various log levels.
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* All of these will print unconditionally, although note that pr_debug()
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* and other debug macros are compiled out unless either DEBUG is defined
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* or CONFIG_DYNAMIC_DEBUG is set.
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*/
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#define pr_emerg(fmt, ...) \
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printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_alert(fmt, ...) \
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printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_crit(fmt, ...) \
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printk(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_err(fmt, ...) \
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printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_warning(fmt, ...) \
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printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_warn pr_warning
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#define pr_notice(fmt, ...) \
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printk(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_info(fmt, ...) \
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printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
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/*
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* Like KERN_CONT, pr_cont() should only be used when continuing
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* a line with no newline ('\n') enclosed. Otherwise it defaults
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* back to KERN_DEFAULT.
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*/
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#define pr_cont(fmt, ...) \
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printk(KERN_CONT fmt, ##__VA_ARGS__)
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/* pr_devel() should produce zero code unless DEBUG is defined */
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#ifdef DEBUG
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#define pr_devel(fmt, ...) \
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printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_devel(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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#include <linux/dynamic_debug.h>
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/* If you are writing a driver, please use dev_dbg instead */
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#if defined(CONFIG_DYNAMIC_DEBUG)
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/* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */
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#define pr_debug(fmt, ...) \
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dynamic_pr_debug(fmt, ##__VA_ARGS__)
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#elif defined(DEBUG)
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#define pr_debug(fmt, ...) \
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printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_debug(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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/*
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* Print a one-time message (analogous to WARN_ONCE() et al):
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*/
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#ifdef CONFIG_PRINTK
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#define printk_once(fmt, ...) \
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({ \
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static bool __print_once __read_mostly; \
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\
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if (!__print_once) { \
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__print_once = true; \
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printk(fmt, ##__VA_ARGS__); \
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} \
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})
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#define printk_deferred_once(fmt, ...) \
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({ \
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static bool __print_once __read_mostly; \
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\
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if (!__print_once) { \
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__print_once = true; \
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printk_deferred(fmt, ##__VA_ARGS__); \
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} \
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})
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#else
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#define printk_once(fmt, ...) \
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no_printk(fmt, ##__VA_ARGS__)
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#define printk_deferred_once(fmt, ...) \
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no_printk(fmt, ##__VA_ARGS__)
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#endif
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#define pr_emerg_once(fmt, ...) \
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printk_once(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_alert_once(fmt, ...) \
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printk_once(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_crit_once(fmt, ...) \
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printk_once(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_err_once(fmt, ...) \
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printk_once(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_warn_once(fmt, ...) \
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printk_once(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_notice_once(fmt, ...) \
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printk_once(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_info_once(fmt, ...) \
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printk_once(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_cont_once(fmt, ...) \
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printk_once(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
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#if defined(DEBUG)
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#define pr_devel_once(fmt, ...) \
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printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_devel_once(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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/* If you are writing a driver, please use dev_dbg instead */
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#if defined(DEBUG)
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#define pr_debug_once(fmt, ...) \
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printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_debug_once(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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/*
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* ratelimited messages with local ratelimit_state,
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* no local ratelimit_state used in the !PRINTK case
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*/
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#ifdef CONFIG_PRINTK
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#define printk_ratelimited(fmt, ...) \
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({ \
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static DEFINE_RATELIMIT_STATE(_rs, \
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DEFAULT_RATELIMIT_INTERVAL, \
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DEFAULT_RATELIMIT_BURST); \
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\
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if (__ratelimit(&_rs)) \
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printk(fmt, ##__VA_ARGS__); \
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})
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#else
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#define printk_ratelimited(fmt, ...) \
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no_printk(fmt, ##__VA_ARGS__)
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#endif
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#define pr_emerg_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_alert_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_crit_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_err_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_warn_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_notice_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_info_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
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/* no pr_cont_ratelimited, don't do that... */
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#if defined(DEBUG)
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#define pr_devel_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_devel_ratelimited(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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/* If you are writing a driver, please use dev_dbg instead */
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#if defined(CONFIG_DYNAMIC_DEBUG)
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/* descriptor check is first to prevent flooding with "callbacks suppressed" */
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#define pr_debug_ratelimited(fmt, ...) \
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do { \
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static DEFINE_RATELIMIT_STATE(_rs, \
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DEFAULT_RATELIMIT_INTERVAL, \
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DEFAULT_RATELIMIT_BURST); \
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DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, pr_fmt(fmt)); \
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if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT) && \
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__ratelimit(&_rs)) \
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__dynamic_pr_debug(&descriptor, pr_fmt(fmt), ##__VA_ARGS__); \
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} while (0)
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#elif defined(DEBUG)
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#define pr_debug_ratelimited(fmt, ...) \
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printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#else
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#define pr_debug_ratelimited(fmt, ...) \
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no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
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#endif
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extern const struct file_operations kmsg_fops;
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enum {
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DUMP_PREFIX_NONE,
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DUMP_PREFIX_ADDRESS,
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DUMP_PREFIX_OFFSET
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};
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extern int hex_dump_to_buffer(const void *buf, size_t len, int rowsize,
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int groupsize, char *linebuf, size_t linebuflen,
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bool ascii);
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#ifdef CONFIG_PRINTK
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extern void print_hex_dump(const char *level, const char *prefix_str,
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int prefix_type, int rowsize, int groupsize,
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const void *buf, size_t len, bool ascii);
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#if defined(CONFIG_DYNAMIC_DEBUG)
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#define print_hex_dump_bytes(prefix_str, prefix_type, buf, len) \
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dynamic_hex_dump(prefix_str, prefix_type, 16, 1, buf, len, true)
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#else
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extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
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const void *buf, size_t len);
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#endif /* defined(CONFIG_DYNAMIC_DEBUG) */
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#else
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static inline void print_hex_dump(const char *level, const char *prefix_str,
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int prefix_type, int rowsize, int groupsize,
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const void *buf, size_t len, bool ascii)
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{
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}
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static inline void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
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const void *buf, size_t len)
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{
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}
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#endif
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#if defined(CONFIG_DYNAMIC_DEBUG)
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#define print_hex_dump_debug(prefix_str, prefix_type, rowsize, \
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groupsize, buf, len, ascii) \
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dynamic_hex_dump(prefix_str, prefix_type, rowsize, \
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groupsize, buf, len, ascii)
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#elif defined(DEBUG)
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#define print_hex_dump_debug(prefix_str, prefix_type, rowsize, \
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groupsize, buf, len, ascii) \
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print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, rowsize, \
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groupsize, buf, len, ascii)
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#else
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static inline void print_hex_dump_debug(const char *prefix_str, int prefix_type,
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int rowsize, int groupsize,
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const void *buf, size_t len, bool ascii)
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{
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}
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#endif
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#endif
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